Effects of tungsten decoration on the performance of a Ni-based oxygen carrier during chemical looping reforming of biogas for hydrogen generation

Journal article, 2023

Biogas, typically containing around 60% CH4and 40% CO2, can be used as feedstock in chemical looping reforming (CLR) process. In our previous work, a Ni-based oxygen carrier (OC) using high-alumina firebrick as support has shown excellent performance of complete CH4 and CO2 conversion of biogas, thus resulting in high H2 and CO yield in CLR. Nonetheless, that work also found that the presence of H2S in biogas can poison the OC and then leads to decrease of the OC reactivity. Based on some literatures, tungsten is promising of lessening the sulfur poisoning on catalysts. In the present work, tungsten was used to decorate the Ni oxygen carrier and the impregnating sequence of Ni and W in the firebrick was changed to study the effects on the OC performance. An 1000µL/L H2S was mixed with the biogas (the ratio of CH4/CO2 was 3/2) and experiments were carried out in a batch fluidized bed reactor under various reacting conditions. It is found that the W-decoration can lower catalytic activity of the oxygen carrier, and the sequence of Ni and W impregnation can also impact the reforming performance. In the case of no H2S mixing, the OC-Ni-W (first with Ni impregnation, then W impregnation) oxygen carrier has better catalytic performance as compared to OC-Ni=W (Ni, W simultaneous impregnation) and OCW-Ni (first W then Ni). With the presence of 1000µL/L H2S, the OC-Ni-W has higher CO and H2 yield as compared to OC-W-Ni and OC-Ni=W.